R adjusting the angular relation between a workpiece to be ground and a tool

ABSTRACT

An automatic taper compensator is used to maintain a parallel relationship between the axis of a wide grinding wheel or multiple grinding wheels (22-26) and the centerline of a cylindrical workpiece (W) on a grinding machine. Two gage heads (43, 44) are automatically advanced during the grinding cycle at the extreme ends of the workpiece portions being ground. A differential circuit (48) directly compares the voltage output of the right hand (R.H.) and the left hand (L.H.) gage heads (43, 44) and generates a signal when the difference varies by more than a predetermined amount. Compensation is effected by deflecting the appropriate wheel spindle bearing support (41 or 41&#39;&#39;) in a forward direction, as separate force applying means (49, 49&#39;&#39;) are provided at each end of the wheel spindle (18) for that purpose.

United States Patent Price 1 Sept. 12, 1972 54] MEANS FOR ADJUSTING THEANGULAR RELATION BETWEEN A WORKPIECE TO BE GROUND AND A TOOL [72]inventor: Ralph E. Price, Waynesboro, Pa.

[73] Assignee: Landls Tool Company [2]] Appl. No.: 98,807

52 us. c1. ..51/165 R, 51/165.9l 51 1m. (:1. ..B24b 49/04 58 Field 0fSearch.5l/l65 R, 165.71, 165.8, 165.9,

5l/l65.91, 165.92, 105 SP [56] References Cited UNITED STATES PATENTS3,064,395 11/1962 Price ..5l/ 165 R 3,097,454 7/1963 Pheil ..5l/ 165 R3,145,508 8/1964 Price ..5lll65.9 3,271,910 9/1966 Haisch ..5l/l65RPrimary Examinerl-larold D. Whitehead Attorney-Joseph R. Spalla [57]ABSTRACT An automatic taper compensator is used to maintain a parallelrelationship between the axis of a wide grinding wheel or multiplegrinding wheels (22-26) and the centerline of a cylindrical workpiece(W) on a grinding machine. Two gage heads (43, 44) are automaticallyadvanced during the grinding cycle at the extreme ends of the workpieceportions being ground. A differential circuit (48) directly compares thevoltage output of the right hand (R.l-l.) and the left hand (Ll-i.) gageheads (43, 44) and generates a signal when the difference varies by morethan a predetermined amount. Compensation is effected by deflecting theappropriate wheel spindle bearing support (41 or 41') in a forwarddirection, as separate force applying means (49, 49') are provided ateach end of the wheel spindle (18) for that purpose.

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MEANS FOR ADJUSTING TI-IE ANGULAR RELATION BETWEEN A WORKPIECE TO BEGROUND AND A TOOL BACKGROUND OF THE INVENTION l. Field Of The InventionThis invention relates to an improved method and apparatus forpreventing a taper from being formed on a workpiece, which is beingground on a multiple grinding wheel machine. The invention also hasapplication on wide wheel grinding machines. In multiple or wide wheelcylindrical grinding machines, it is very important to maintain aparallel relationship between the axis of the workpiece and the axis ofthe grinding wheel(s). Otherwise, the workpiece can be ground with ataper, i.e., one end of the workpiece is ground oversize in relation tothe other. It is desirable that adjustments be made to the relativepositions of the wheel(s) and workpiece(s) during the grinding cycle inorder to provide finished pieces which are ground to the same toleranceover the entire length thereof. This invention has particularapplication in grinding workpieces such as automotive crankshaftswherein the main bearings are ground on an automatic machine havingmultiple wheels, spaced according to the bearings.

2. Description Of The Prior Art Prior to this invention, gaging meanswere provided for measuring spaced diameters on a workpiece. Facilitieswere provided to stop the grinding operation if one of the diameters wasground to a low limit before the other diameter had been ground to ahigh limit. The taper was then corrected by adjusting a swivel table aslight amount to compensate for the measured taper. An example of thismethod was covered in the Pheil U.S. Pat. No. 3,097,454, granted JulyI6, 1963. This method is used on manual machines and would not besatisfactory for automatically-operated machines.

In the Haisch U.S. Pat. No. 3,271,910, granted Sept. 13, 1966, aparallel or a predetermined angular position between the axis of agrinding wheel spindle and the axis of the workpiece was controlledautomatically. In the only operative embodiment disclosed in thispatent, the headstock (or tailstock, but not both) was displaced tocompensate for any resulting taper. This approach has the drawback thatthe movement of the headstock (or tailstock) can interfere with the workrest positioned adjacent thereto. It should also be noted that if anyover-correction occurs, contact between the grinding wheel and theworkpiece would be lost, since the headstock (or tailstock) then had tobe retracted. This has the disadvantage of disturbing the spatialrelationship between the workpiece and the wheel, causing further gagingproblems.

SUMMARY OF THE INVENTION In accordance with the invention, a multiple orwide wheel grinding machine is provided for grinding axially spacedportions of a workpiece. The machine includes a work support forsupporting the workpiece and the grinding wheel support including aspindle for supporting one or more rotatably mounted grinding wheels.Means are provided to effect a relative transverse feeding movementbetween the wheel spindle and the workpiece support to perform agrinding operation. At least two electrical size signals are generatedfrom spaced portions on the workpiece during the grinding cycle.

The two signals are compared directly and a third signal is generatedwhen the difference between the signals exceeds a predetermined value.The third signal actuates means for deflecting the wheel support to movethe corresponding grinding wheel toward the workpiece.

In the preferred embodiment, separate and independent means are providedat spaced portions of the grinding wheel, to displace one or the otherof the spindle supports in a transverse direction. In order tofacilitate the deflection of the spindle supports, the supports are inthe form of cantilever arms which can be deformed in a forward directiontoward the workpiece.

It is, therefore, an object of the present invention to control aparallel relationship between the axis of the wheel spindle and the axisof the workpiece automatically.

Another object is to provide a control device which directly comparesthe voltage output from two gages to each other and generates a tapercompensating signal in response thereto.

Another object is to remove all compensation from the workpiece, whichenables the original setting of the headstock, tailstock, work rests,and the gage heads to be undisturbed during the complete grinding cycle.

Another object is to maintain a parallel relationship between the axisof the wheel spindle and the axis of the workpiece, without interferingwith the support of pressure from a work rest.

Another object is to provide a means for compensating for any taperautomatically, without losing contact between the grinding wheel and thesurface of the workpiece.

Another object is to enable any over-compensation to be corrected byeffecting movement of the opposite taper compensating mechanism, withoutlosing contact between the grinding wheel and the surface of theworkpiece.

Another object is to provide means to reset the position of the grindingwheel spindle to its original parallel position at completion of eachgrinding cycle autom atically.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a plan view of a multiplewheel grinding machine, embodying the present invention, and showingtaper compensation mechanisms for advancing either end of the grindingwheel spindle, the visual readout dials from the gage system, and theschematic diagram showing the hydraulic controls, and

FIG. 2 is a partial R.H. end view showing the RH. taper compensationmechanism mounted on the wheel support, and the differential circuit ofthe gage system, and

FIGS. 3A and 3B are a diagram showing the circuit logic for the tapercompensation mechanisms.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings,in FIG. I, there is illustrated the plan view of a grinding machine,generally designated by the numeral 10, having a bed 11, which supportsa wheel support 12 and a work support 13. The wheel support 12 carriesthe spindle bearings 16 and I7, which support the rotatable spindle 18.The

spindle bearings are retained in a spaced relation by means of R.H. andLil. clamps, l9 and 20, which are pivotably mounted, but secured to thefront of the wheel support 12. through fasteners 21. Grinding wheels 22,23, 24, 2S, and 26 are carried in a spaced relation to correspond to theportions of the workpiece W to be ground, by means of spacers 27, 28,29, 30,31 and 32, which are locked in position by wheel center rings 33and 34.

The workpiece W is rotatably supported by the headstock and tailstockwork centers 36 and 37 in a conventional manner. The headstock 38 andthe tailstock 39 are longitudinally positioned and locked to the worksupport 13, and the work support 13 is manually positioned to align theworkpiece portions with the spaced grinding wheels 22-26.

The front portion of the wheel support 12 includes wheel spindlesupports 41 and 41' which are longitudinally spaced to form the rearsupport for the spindle bearings 16 and 17 at the respective locations.As shown in H6. 2, the wheel spindle support 41 is connected to thewheel support 12 at its lower end, but is unsupported at its upper end,the wheel support 41 is formed in a similar manner. The supports 41 and41' act as cantilever arms which can be deflected to change the angularposition of the wheel spindle 18 with respect to the workpiece W. Theappropriate support 41 or 41' is deflected automatically during a dwellin the grinding cycle to insure a parallel relationship between the axisof the wheel spindle l8 and the axis of the workpiece W prior toreaching size.

An electronic grinding gage system 42 consists of two gage heads 43 and44 having readout dials 46 and 47 which receive signals fromconventional probe members or transducers 45 and 45' and also directs asignal to a differential comparator circuit 48, which compares allreadings directly through a continuous plus or minus reading from anormal zero setting as indicated by a differential dial 50, describedmore fully hereinafter. (The gage system 42 is similar to the electronicgage Model l35B-79 R-l shown in a catalogue of Federal ProductsCorporation, 1144 Eddy Street, Providence, Rhode Island 02901.) Thedifferential comparator circuit 48 includes two oscillators (not shown)which transmit signals through linear variable differential transformersto the transducers 45 and 45'. The transducers 45 and 45' send voltagesignals back to the differential comparator circuit 48, the voltages ofwhich are a function of the position of the transducers. The signals aredirectly compared in the differential comparator circuit 48, and ifthere is a differential between the voltages which exceeds apredetermined amount, one of two relays (not shown) within thedifferential comparator circuit 48, is energized. A first of the relayshas a contact CR1 and a second of the relays has a contact CR2 (see FIG.2). This circuit 48 is used to make taper corrections by advancing therespective end of the wheel spindle l8 automatically to compensate forany undesired taper between the ends of the workpiece W, when thetolerance limits are exceeded.

Each end of the spindle 18 is advanced by the movement of a tapercompensator assembly 49 and 49', to compensate for the oversize diameterportion. The taper compensation assemblies 49 and 49 are secured to eachside of the wheel support 12, as shown in FIG. 1.

The RH. and L.l-l. taper compensating mechanisms are identical,therefore, only the R.H. assembly 49 will be described. The right handend of the wheel spindle 18 is advanced when the diameter of the righthand end of the workpiece W exceeds the tolerance over the left handdiameter. The forward movement is effected by movement of a piston 51,within a hydraulic cylinder 52, which s secured to a R.l-l. housing 53,through an adaptor plate 54. The RJ-l. housing 53 houses a busing 56,which supports a slidable plunger 57. The plunger 57 is in threadedengagement with a pinion nut 58. The outer teeth 59 of the pinion nut 58are in mesh with the teeth of a rack member 61 which is secured to apiston rod 62 of the piston 51. A threaded portion 60 of the pinion nut58 is in threaded engagement with the internal threads of the bushing56, to provide a fine advance movement of the plunger 57, by means ofdifferential threads.

The bushing 56 includes a vertical slot 63, as shown in FIG. 2, whichenables a key 64 to be secured to the plunger 57, to prevent the plunger57 from rotating when the pinion nut 58 is rotated. The sides of theslot 63 also provide means to limit the total amount of movement of theplunger 57 in either direction.

Movement of the piston rod 62 effects movement of the rack member 61,and the pinion nut 58 is rotated, which advances the pinion nut 58 tothe left, as shown in FIG. 2. The plunger 57 is retracted to the rightrela tive to the pinion nut 58. However, by varying the threads per inchon the nut 58 and the plunger 57, it is possible to advance the nut 58at a faster rate than the plunger 57 retracts, thereby giving theplunger 57 an absolute advance to the left (FIG. 2) at a fine ratethrough differential threads. For example, the nut 58 may have 8 threadsper inch, and the plunger 10 threads per inch. Therefore, the plunger 57is advanced against a pressure post 66, that is secured to the wheelspindle support 41. Movement of the plunger 57 deflects the wheelspindle support 41 a slight amount, and the RH. bearing 16 and the RH.end of the spindle 18 are advanced until the signals from the gage heads43 and 44 come within the allowed tolerance as determined by thedifferential comparator circuit 48. The normal fine feed rate is theninitiated and continues until size is reached.

It should be understood that the control means which effects theoperation of the taper compensating mechanisms 49 and 49' are notactuated until after the wheel support 12 has been advanced by any ofthe conventional means. The gage heads 43 and 44 are not advanced toengage the workpiece diameters until the diameter of the workpiece W hasbeen rough ground. This method is conventional and prevents the gageheads 43 and 44 from being damaged by the rough surface of an ungroundworkpiece.

OPERATION The grinding wheels 22-26 or a single wide wheel (not shown)are advanced by a digital feed system which effects movement of thewheel support 12 for predetermined distances and at predetermined rates,after the workpiece W has been properly positioned in alignment with thegrinding wheels 22-26, and after the headstock 38 has started therotation of the workpiece W. A feed system of this type is disclosed inco-pending application of Price et al., Ser. No. 45,829, filed on June12, 1970, entitled "Feed Rate And Positioning Control System For AMachine Tool," assigned to Landis Tool Co., which is expresslyincorporated herein.

A sequence control counter disclosed in the above patent applicationdetermines the rate of infeed, the end points, and the dwell periodsduring the grinding operation, by controlling the rate and the number ofpulses directed to the electro-hydraulic pulse motor. The pulse motoradvances the grinding wheels 22-26 transversely at preselecteddistances, until a size signal is obtained by means of the gage heads 43and 44.

The grinding wheels are advanced at a rapid infeed rate, until a loadcontrol relay (not shown) is deenergized by contact between the grindingwheels 22-26 and the workpiece W. This reduces the infeed rate of thegrinding wheels 22-26 to a first grinding feed rate. The work rests 67and 68 are advanced to compensate for the resultant forces from thegrinding wheels 22-26, to prevent deflection of the workpiece W in aconventional manner. The grinding feed rate continues until a dwellperiod is effected.

The gage heads 43 and 44 are then advanced to a position as shown inFIG. 1 in the following manner. A gage advance solenoid 1P SOL isenergized which shifts a control valve 79 to the left, and fluidpressure is directed through a line 80 to the valve 79 and to the headend of the hydraulic motors or cylinders 81 and 82 through lines 83, 83aand 83b. Flow control valves 86 and 87 are included in the lines 83a and83b, respectively, to control the operating speed of pistons 88 and 89,by throttling the pressure and by allowing free flow of the returningfluid. Fluid pressure from the lines 83, 83A, and 83B advances thepistons 88 and 89, which advance the gage heads 43 and 44, respectively,against the end portions of the workpiece W. The lines 90 and 90A directthe fluid being exhausted from the rod end of the cylinders 81 and 82through the valve 79 and to a drain 85.

The wheel support 12 is retracted a small amount at the end of a firstdwell period, until the counter is equal to the number set on the resetswitches (not shown). The grinding wheels 22-26, are advanced after asecond dwell period and a second feed rate is effected which continuesuntil either of the No. 2 gage contacts on the dial 46 or 47 aretripped, to effect the third dwell period.

Taper compensation will be effected automatically during the third dwellperiod, by the energization of the RH. or L.H. taper compensationsolenoids HA SOL or 11HA SOL, respectively, if the comparator circuit 48indicates a predetermined difference between the RH. and the LR.portions of the workpiece W.

In the case of right hand compensation, the contact CR1 in a line 69(FIG. 2) is closed by energization of its associated relay (not shown)in the comparator circuit 48. A circuit is completed to a converter 72which converts the voltage to a logic level, and through a SchmittTrigger 74 which squares the pulse waves in a conventional manner, toprovide a signal that the RH. diameter is over the tolerance range.(Left hand compensation is similarly effected through closure of contactCR2 in a line 71 which completes a circuit through a converter 73 and aSchmitt Trigger 75.)

When the taper compensation switch S510 is in the ON position, tapercompensation will be effected to advance the RH. end of the wheelspindle 18. This occurs when the signal from the comparator circuit 48determines that the diameter of the RH. portion of the workpiece W asmeasured by the transducer 45 of the R.I-I. gage head 43, exceeds theallowable tolerance over the diameter being measured by the transducer45 of the L.H. gage head 44.

Referring to FIGS. 3A and 3B, the solenoid IOHA SOL is energized when asignal from an expander 91 is directed to an AND gate 92 through a line93 and the AND gate 92 directs a signal to an AND gate 97 through a line94. A signal is directed from the AND gate 97 to an output converter 98through a line 99. The output converter 98 converts the d-c voltagesignal to an a-c voltage signal and energizes the solenoid 10I-IA SOL,which is protected by conventional fuses (unnumbered).

The energization of the solenoid 10HA SOL shifts a control valve 100 tothe right (FIG. 1). Main pressure from a hydraulic source directshydraulic fluid from a line 101 through the valve 100, and through aline 102, which connects the valve 100 to the head end of the hydrauliccylinder 52. A flow control valve 103 is included in the line 102 tocontrol the operating speed of the piston 51 within the cylinder 52 bythrottling the fluid pressure and by allowing free flow of the returningfluid when the piston 51 is reset. The piston 51, the piston rod 62, andthe rack member 61 which are in mesh with the outer teeth 59 of thepinion nut 58, are advanced. This movement effects rotation of the nut58 which advances to the left (FIG. 2), and the plunger 57 is retractedto the right at a slower rate. Therefore, the pinion nut 58 drives theplunger 57 against the post member 66, at a line feed rate, whichdeforms or deflects the wheel spindle support 41, to effect the forwardmovement of the RH. end of the wheel spindle 18.

Referring now to FIG. 1, it should be understood that the line 104directs the fluid being exhausted from the rod end of the cylinder 52through the valve 100, and to a line 105 which is connected to a drain106.

Movement of the plunger 57 continues, until the comparator circuit 48determines that the signals returning from the transducers 45 and 45'are within a specified limit, as visually indicated by the differentialdial 50. The contact CR1 is opened and solenoid 10I-IA SOL is thendeenergized, whereupon the control valve 100 is returned to its normalposition by spring pressure.

The fine feed rate is started at completion of the third dwell period.The grinding wheels 22-26 are advanced at a slow rate until either ofthe No. 3 gage contacts, as shown on the readout dials 46 and 47(FIG. 1) are tripped. The fourth dwell period is effected and a sparkoutoperation is effected which continues until size is obtained. The wheelsupport 12 is retracted in a conventional manner when size is reachedand the RH. taper compensating assembly 49 is reset. The reset movementis effected by the energization of the solenoid 10I-IB SOL, which occurswhen the RH. compensation flip-flop 107 (FIG. 3A) is reset. This occurswhen the line 108 directs a signal to the a-c converter 109, whichconverts the d-c voltage signal to an a-c voltage signal, and energizesthe RH. compensation reset solenoid 10HB SOL.

The RP]. compensation flip-flop 107 is reset when a signal from theexpanders 76 and 77 are directed to the AND gate 78 which directs asignal to the flip-flop 107 through a line 84, following a delay afterthe grinding cycle is completed. The flip-flop 107 is also reset shouldthe footstock 39 be retracted, as an expander 95 will provide a signalto the AND gate 78 which is connected to the flip-flop 107 through theline 84.

The energization of the solenoid HB SOL shifts the control valve 100(H0. 1) to the left, and hydraulic fluid is directed from the line 101through the valve 100, and through the line 104, to the rod end of thecylinder 52. The piston 51 and the piston rod 62 are reset and the rackmember 61 rotates the pinion nut 58 to retract the plunger 57 to thereset or original position. The axis of the wheel spindle 18 is returnedto its normal free position which is parallel to the axis of theworkpiece W.

It should be understood that the operation of the L.H. tapercompensation assembly 49 as shown in FIG. 1, is effected in a similarmanner, should the comparator circuit 48 determine that the diameter ofthe L.H. portion of the workpiece W, as measured by the transducer 45'of the L.H. gage head 43, exceeds the allowable tolerance over thediameter being measured by the transducer 45 of the RH. gage head 43.The L.H. compensation advance solenoid Ill-IA SOL is energized, and thecontrol valve 111 is shifted to-the right. Fluid pressure is directedthrough the lines 101 and 101A, through the valve 111 to a line 112,which is connected to the head end of the cylinder 52'. A flow controlvalve 113 is included in the line 112 to control the operating speed ofthe piston 51' within the cylinder 52' by throttling the fluid pressureand by allowing free flow of the returning fluid when the piston 51' isreset. it should be understood that the line 114 directs the fluid beingexhausted from the rod end of the cylinder 52' through the valve 111, toa line 116 which is connected to the line 105 and drain 106.

Taper compensation is then effected in the manner as previouslydescribed, and the L.H. side of the wheel spindle support 41' isdeflected to advance the L.H. end of the wheel spindle 18, until thesignals returning from the transducers 45 and 45' are within specifiedlimits. Fine feed is then started and the wheel support 12 is advancedat a fine feed rate until size is reached.

The wheel support 12 is retracted in a conventional manner following adelay after size is reached, and the L.H. compensating reset solenoidllHB SOL is energized. The control valve 111 is shifted to the left, andhydraulic fluid from the lines 101 and 101A is directed through thevalve 111 and to the rod end of the cylinder 52, through the line 114.The piston 51 is reset, and the plunger 57' is retracted to its resetposition in preparation for grinding the next workpiece W.

The control circuit in FIG. 3B for L.H. taper compensation is similar toFIG. 3A for RH. taper compensation, and like elements have been givenlike numerals with a prime designation.

It should be understood that the fine feed rate is stopped at any time,should the comparator circuit 48 determine that the difference betweenthe RH. and L.H. portions of the workpiece W indicates a taper. A signalis directed from the AND gate 92 to an AND gate 118 through a line 119when a signal for RH.

compensation is generated. A signal from an AND gate 92' directs asignal through a line 121 to the expander 122 and to the AND gate 118when a signal for L.H. compensation is generated. The R.H. or L.H.compensation is otherwise effected as previously stated.

While this invention is described in detail with reference to automaticmeans for maintaining a parallel relationship between the grinding wheelaxis and the centerline of a cylindrical workpiece W, it should beunderstood that the operation of the taper compensation assemblies 49and 49' may also be manually effected or reset during a manual grindingoperation by means of the RH. compensation selector switch SS9, and bythe L.H. compensation selector switch $511, as shown in FIG. 3. Each ofthese switches would provide a signal to the respective AND gates 97 or97'.

It is also to be understood that only a preferred embodiment of theinvention has been specifically illustrated and described, andvariations may be made thereto without departing from the invention, asdefined in the appended claims.

lclaim:

1. In a grinding machine for grinding axially spaced portions of aworkpiece, including a work support for supporting said workpiece, agrinding wheel support including a spindle for supporting a grindingapparatus including at least one rotatably mounted grinding wheel,axially spaced spindle bearings for supporting opposite ends of saidgrinding wheel spindle, means for effecting a relative transversefeeding movement between said wheel spindle and said work support toperform a grinding operation, the improvement comprising:

said grinding wheel support includes a cantilever arm at each end forsupporting said spindle;

means for generating at least first and second electrical signals fromfirst and second spaced positions on the workpiece during the grindingcycle, said signals being representative of the dimension of theworkpiece at said first and second positions;

means for directly comparing said first and second signals andgenerating a third signal when the difference between said signalsexceeds a predetermined value; and

means actuated by said third signal for deflecting one of saidcantilever arms of the wheel support to move the end of said grindingapparatus corresponding to the higher of said first and second signalstoward the workpiece to bring the grinding wheel spindle intoparallelism with the workpiece.

2. A grinding machine as recited in claim 1, wherein said deflectingmeans includes two separate force applying mechanisms, one of each endof the wheel support, for moving the grinding wheel spindle toward theworkpiece.

3. A grinding machine as recited in claim 1, wherein said plungers havethreads at one end, and wherein said force applying mechanisms eachfurther comprises:

a hydraulic motor having a piston rod with a rack member formed in theend thereof, said motor being operable in response to said third signal;

a pinion nut having internal threads for receiving said one end of saidplunger and having external teeth in mesh with said rack member, andfurther having external threads adjacent the external teeth; and

means in threaded engagement with said external threads of said pinionnut, when the nut is rotating by said rack member, for advancing saidnut and plunger toward said wheel support at one rate while said plungerretracts on the internal threads of said pinion nut at a slower rate, sothat said plunger has an absolute advance into said wheel support uponthe operation of said hydraulic mo- I01.

4. In a grinding machine for grinding axially spaced portions of aworkpiece, including a work support for supporting said workpiece, aspindle for supporting a grinding apparatus including at least onerotatably mounted grinding wheel, axially spaced spindle bearings forsupporting opposite ends of said grinding wheel spindle, feeding meansfor effecting a relative transverse feeding movement between said wheelspindle and said work support to perform a grinding operation, means forcontrolling said feeding means, the improvement comprising:

a grinding wheel spindle support including a pair of cantilever mountedarms for supporting opposite ends of said spindle;

separate and independently movable means associated with said cantileverarms of said grinding wheel spindle for advancing the respective ends ofsaid spindle supports in a transverse direction during a grinding cycle;

means for gaging the workpiece at spaced axial positions and generatingsignals indicative of the relative size of the workpiece at said points;and

means for directly comparing said signals and operable in response tothe gaging means for generating another signal whenever the relativesize of two positions varies more than a predetermined amount, saidsignal being effective to actuate said displacing means to move the endof said spindle corresponding to the larger size workpiece toward theworkpiece until said gaging means determines that the relative sizes ofthe two positions of the workpiece are within said predetermined amount.

5. A grinding machine as recited in claim 4, wherein said displacingmeans comprises:

a hydraulic motor having a piston rod with a rack member formed in theend thereof, said motor being operable in response to said signal;

a plunger having one end associated with said grinding wheel support andbeing threaded on the other end;

a pinion nut having internal threads for receiving the threaded end ofsaid plunger and having external teeth in mesh with said rack member,and further having external threads adjacent the external teeth; and

means in threaded engagement with said external threads of said pinionnut, when the nut is rotating by said rack member, for advancing saidnut and plunger toward said wheel support at one rate while said plungerretracts on the internal threads of said pinion nut at a slower rate, sothat said plunger has an absolute advance into said wheel support uponthe operation of said hydraulic motor.

6. A grinding machine as recited in claim 4, wherein said a 'n means comrises:

tra ns iu ers posmongd at said spaced axial posmons for generatingelectrical voltages which are a fu nction of the dimensions at therespective positions;

and wherein said displacing means further comprises,

spaced plungers for deflecting the end of said grinding wheel supportcorresponding to the higher of said electrical voltages; and

means, including a hydraulic motor, for advancing one of said plungersin response to said other signal.

7. A grinding machine as recited in claim 4, wherein,

said force applying mechanisms include plungers for deflecting one ofsaid arms upon generation of said signal.

8. In a grinding machine for grinding axially spaced portions of aworkpiece including a work support for supporting said workpiece, agrinding wheel support including a spindle for supporting a grindingapparatus including at least one rotatably mounted grinding wheel,feeding means for effecting a relative transverse feeding movementbetween said wheel spindle and said work support to perform a grindingoperation, means for controlling said feeding means, the improvementcomprising:

said grinding wheel support having axially spaced cantilevered portionsextending therefrom to support said spindle,

means for gaging the workpiece at spaced positions thereof and forgenerating at least two electrical signals indicative of the workpiecediameters at said positions, during the grinding cycle;

means for directly comparing said two signals and generating acompensation signal whenever the signal indicates the axes of thegrinding wheel spindle and workpiece are out of parallelism by more thana predetermined amount; and

force applying means actuated by the generation of said compensationsignal for deflecting one of the cantilevered portions of said wheelsupport toward the workpiece to bring the axes of the grinding wheelspindle and the workpiece into parallelism.

1. In a grinding machine for grinding axially spaced portions of aworkpiece, including a work support for supporting said workpiece, agrinding wheel support including a spindle for supporting a grindingapparatus including at least one rotatably mounted grinding wheel,axially spaced spindle bearings for supporting opposite ends of saidgrinding wheel spindle, means for effecting a relative transversefeeding movement between said wheel spindle and said work support toperform a grinding operation, the improvement comprising: said grindingwheel support includes a cantilever arm at each end for supporting saidspindle; means for generating at least first and second electricalsignals from first and second spaced positions on the workpiece duringthe grinding cycle, said signals being representative of the dimensionof the workpiece at said first and second positions; means for directlycomparing said first and second signals and generating a third signalwhen the difference between said signals exceeds a predetermined value;and means actuated by said third signal for deflecting one of saidcantilever arms of the wheel support to move the end of said grindingapparatus corresponding to the higher of said first and second signalstoward the workpiece to bring the grinding wheel spindle intoparallelism with the workpiece.
 2. A grinding machine as recited inclaim 1, wherein said deflecting means includes two separate forceapplying mechanisms, one of each end of the wheel support, for movingthe grinding wheel spindle toward the workpiece.
 3. A grinding machineas recited in claim 1, wherein said plungers have threads at one end,and wherein said force applying mechanisms each further comprises: ahydraulic motor having a piston rod with a rack member formed in the endthereof, said motor being operable in response to sAid third signal; apinion nut having internal threads for receiving said one end of saidplunger and having external teeth in mesh with said rack member, andfurther having external threads adjacent the external teeth; and meansin threaded engagement with said external threads of said pinion nut,when the nut is rotating by said rack member, for advancing said nut andplunger toward said wheel support at one rate while said plungerretracts on the internal threads of said pinion nut at a slower rate, sothat said plunger has an absolute advance into said wheel support uponthe operation of said hydraulic motor.
 4. In a grinding machine forgrinding axially spaced portions of a workpiece, including a worksupport for supporting said workpiece, a spindle for supporting agrinding apparatus including at least one rotatably mounted grindingwheel, axially spaced spindle bearings for supporting opposite ends ofsaid grinding wheel spindle, feeding means for effecting a relativetransverse feeding movement between said wheel spindle and said worksupport to perform a grinding operation, means for controlling saidfeeding means, the improvement comprising: a grinding wheel spindlesupport including a pair of cantilever mounted arms for supportingopposite ends of said spindle; separate and independently movable meansassociated with said cantilever arms of said grinding wheel spindle foradvancing the respective ends of said spindle supports in a transversedirection during a grinding cycle; means for gaging the workpiece atspaced axial positions and generating signals indicative of the relativesize of the workpiece at said points; and means for directly comparingsaid signals and operable in response to the gaging means for generatinganother signal whenever the relative size of two positions varies morethan a predetermined amount, said signal being effective to actuate saiddisplacing means to move the end of said spindle corresponding to thelarger size workpiece toward the workpiece until said gaging meansdetermines that the relative sizes of the two positions of the workpieceare within said predetermined amount.
 5. A grinding machine as recitedin claim 4, wherein said displacing means comprises: a hydraulic motorhaving a piston rod with a rack member formed in the end thereof, saidmotor being operable in response to said signal; a plunger having oneend associated with said grinding wheel support and being threaded onthe other end; a pinion nut having internal threads for receiving thethreaded end of said plunger and having external teeth in mesh with saidrack member, and further having external threads adjacent the externalteeth; and means in threaded engagement with said external threads ofsaid pinion nut, when the nut is rotating by said rack member, foradvancing said nut and plunger toward said wheel support at one ratewhile said plunger retracts on the internal threads of said pinion nutat a slower rate, so that said plunger has an absolute advance into saidwheel support upon the operation of said hydraulic motor.
 6. A grindingmachine as recited in claim 4, wherein said gaging means comprises:transducers positioned at said spaced axial positions for generatingelectrical voltages which are a function of the dimensions at therespective positions; and wherein said displacing means furthercomprises, spaced plungers for deflecting the end of said grinding wheelsupport corresponding to the higher of said electrical voltages; andmeans, including a hydraulic motor, for advancing one of said plungersin response to said other signal.
 7. A grinding machine as recited inclaim 4, wherein, said force applying mechanisms include plungers fordeflecting one of said arms upon generation of said signal.
 8. In agrinding machine for grinding axially spaced portions of a workpieceincluding a work support for supporting said workpiece, a grinding wheelsupport including a spiNdle for supporting a grinding apparatusincluding at least one rotatably mounted grinding wheel, feeding meansfor effecting a relative transverse feeding movement between said wheelspindle and said work support to perform a grinding operation, means forcontrolling said feeding means, the improvement comprising: saidgrinding wheel support having axially spaced cantilevered portionsextending therefrom to support said spindle; means for gaging theworkpiece at spaced positions thereof and for generating at least twoelectrical signals indicative of the workpiece diameters at saidpositions, during the grinding cycle; means for directly comparing saidtwo signals and generating a compensation signal whenever the signalindicates the axes of the grinding wheel spindle and workpiece are outof parallelism by more than a predetermined amount; and force applyingmeans actuated by the generation of said compensation signal fordeflecting one of the cantilevered portions of said wheel support towardthe workpiece to bring the axes of the grinding wheel spindle and theworkpiece into parallelism.